Reducing Trihalomethane

Levels in Drinking Water

A Major Qualifying Project Submitted to the Faculty of

WORCESTER POLYTECHNIC INSTITUTE

In partial fulfillment of the requirements

for the Degree of Bachelor of Science By

Brooke Cotta Mariana De Obaldia Caryn MacDonald

Jamie Pierce

Presented to Professor Jeannine Plummer

Advisor

March 6, 2014

Project: JYP-1301

Abstract

Chemical disinfection is a vital part of treating drinking water to protect human health against waterborne diseases. However, chlorine can react with organic matter to produce disinfection byproducts (DBPs) which can heighten the risk of cancers and reproductive complications. The goal of this project was to reduce DBP precursors in the drinking water of the Town of Dartmouth, MA for compliance with the U.S. Environmental Protection Agency (EPA) Disinfectants and Disinfection Byproduct Rule (DBPR). The town is concerned with trihalomethanes (THMs), a DBP regulated by both the U.S. EPA and Massachusetts Department of Environmental Protection (MassDEP). The town obtains its drinking water from 13 groundwater wells. Water is treated at one of three water treatment plants by chlorine disinfection, Greensand filtration for iron and manganese removal (with the addition of a polymer coagulant), and corrosion control. Water quality analysis showed that total organic carbon (TOC) levels in the raw well water ranged from 0.8 to 7.5 mg/L, while TOC in the distribution system was 1.1 - 2.5 mg/L. A bench scale filtration column was designed to mimic the current treatment processes at the plant. Raw water was collected from the wells with the highest TOC levels for testing. Bench scale experiments included treatment of water with chlorine, sodium hydroxide, and/or polymer coagulant, and then filtration through Greensand, GreensandPlus, and/or anthracite. The goal of the experiments was to determine optimal conditions for TOC/DOC reduction while maintaining adequate iron and manganese removal. Based on water quality analysis, bench scale experiments, and literature research, it was recommended that the Dartmouth Water Division upgrades its treatment plant to GreensandPlus and reduce its pre-chlorination dose to result in half of the current chlorine residual. Through this final experiment, a TOC level of 1.6 mg/L was achieved as well as meeting the secondary standard for iron and manganese.

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Executive Summary Though disinfection of drinking water has proved to be crucial in protecting human health, the addition of chemical disinfectants is known to cause disinfection byproducts (DBPs) that are potentially carcinogenic and pose other health risks. The United States Environmental Protection Agency (U.S. EPA) and the Massachusetts Department of Environmental Protection (MassDEP) both regulate DBPs under the U.S. EPA’s Disinfectants and Disinfection Byproduct Rule (DBPR). The Town of Dartmouth, Massachusetts has exceeded levels of trihalomethanes (THMs), a regulated DBP in August 2013. The Town of Dartmouth obtains its drinking water from 13 groundwater wells and treats it at three town-operated water treatment plants. Water treatment consists of disinfection with sodium hypochlorite, pH adjustment with sodium hydroxide, polymer coagulant and filtration through Greensand and GreensandPlus media for iron and manganese removal. The goal of this project was to recommend solutions for THM precursor reduction in drinking water from the Town of Dartmouth, while maintaining adequate iron and manganese removal. The THM precursors targeted were total organic carbon and dissolved organic carbon (TOC/DOC). In order to determine raw groundwater TOC/DOC levels, samples were collected at each of the 13 wells in Dartmouth. Sampling was conducted three times over a five month period for each parameter. Temperature and pH were also measured, as these parameters affect THM formation. Water quality analysis showed that TOC levels in the raw well water ranged from 0.8 to 7.5 mg/L and the DOC levels ranged from 1.1 to 6.7 mg/L. The highest TOC/DOC levels were associated with the Violetta wells. Water obtained from the Violetta wells is treated at 579 Old Westport Road Treatment Plant in Dartmouth. This finding allowed the focus of this study to be on the 579 Old Westport Road Treatment Plant for developing solutions for THM reduction. Water samples were also taken in nine distribution system locations based on the routine sampling locations for the Dartmouth Treatment Plant. TOC in the distribution system ranged from 1.1 - 2.5 mg/L, while DOC ranged from 1.2 - 2.8 mg/L. In order to determine methods for TOC/DOC reduction, a bench scale filtration column was designed to mimic the current treatment processes at the 579 Old Westport Road plant. Raw water was collected at the treatment plant and used for testing. Bench scale experiments included treatment of water with sodium hypochlorite, sodium hydroxide, polymer coagulant, and/or aluminum sulfate and then filtration through Greensand, GreensandPlus, and/or anthracite. Ten filtration column experiments were conducted to determine optimal operating conditions for removal of TOC/DOC, while also meeting iron and manganese guidelines. The filtration column was run for two hours, with samples collected every fifteen minutes.

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Results of the bench scale experiments showed that the parameters used by the Dartmouth Treatment Plant did not reduce TOC or DOC compared to the raw water concentration. While the iron concentration was below the secondary standard, the manganese concentration was too high. Based on the ten experiments, only the GreensandPlus and anthracite experiment met both the iron and manganese secondary standards after the water was run through the filter. The same experiment reached a TOC removal of 14.8% and a DOC removal of 18.0%, which is optimal for treatment. An experiment with half of the chlorine residual also showed favorable TOC and DOC reduction and met the iron secondary standard. Adding additional polymer, increasing or decreasing the pH, and adding alum did not show adequate removal. Given these results, GreensandPlus and anthracite, a pH of 8.1-8.2, a chlorine residual of 0.2 mg/L and a 1.5-1.9 mg/L dose of polymer were parameters chosen for a final experiment. The results of the final experiment confirmed that the chosen parameters gave the most desirable results. TOC was reduced by 10.2% and DOC was reduced by 16.1%. Iron and manganese levels both met the U.S. EPA guidelines, at concentrations of 0.081 and 0.031, respectively. The current base cost of running six Greensand and anthracite filtration units (not including the cost of gravel) is approximately $2,800 per year and upgrading to GreensandPlus and anthracite units would cost $4,400 per year. These calculations are based on the fact that Greensand has a life span of 5-8 years and GreensandPlus lasts 10-15 years. Considering costs for media, sodium hypochlorite, sodium hydroxide, and polymer, the current annual treatment plant costs are approximately $37,000. The final experiment would cost approximately $39,000 per year, a 5.4% increase. These prices do not include the cost of sodium hypochlorite and sodium hydroxide used to adjust the pH of the post-filter water before being discharged into the distribution system. Due to the limited scope of this project, multiple recommendations for moving forward are suggested. It is recommended that pilot testing of suggested design upgrades is conducted, and a full cost analysis should be completed. A reassessment of the chlorine contact time is also recommended if the suggested lower chlorine residual is implemented in order to be in compliance with the U.S. EPA. The Dartmouth Water Division should also consider alternative DBP removal options including changes to the distribution system, such as an addition of a SolarBee mixing tank, and comparing costs to the suggested treatment plant upgrades.

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Acknowledgements Our team acknowledges the help of many people throughout the course of our project. First, we would like to thank the water treatment plant operators in the Town of Dartmouth, MA for assisting us in sample collection, providing us information regarding their water treatment process and donating filtration media for our laboratory experiments. For the construction of our bench scale filtration column, we would like to thank Russ Lang. We would like to thank Don Pellegrino and Patrick Malone for their laboratory assistance. In addition, we would like to thank Hungerford & Terry for their donation of filtration media. Lastly, we would like to thank our advisor, Jeanine Plummer, for her guidance and technical recommendations throughout the course of the project. Without the contributions of these people, the success of our project would not have been possible.

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Table of Contents

Abstract ............................................................................................................................................ i Executive Summary ........................................................................................................................ ii Acknowledgements ........................................................................................................................ iv List of Figures .............................................................................................................................. viii List of Tables ................................................................................................................................. ix Acronyms ........................................................................................................................................ x 1.0 Introduction ............................................................................................................................... 1 2.0 Background ............................................................................................................................... 2

2.1 Disinfection Byproducts in Drinking Water ......................................................................... 2 2.1.1 Types of Disinfection Byproducts .................................................................................. 2

2.2 Disinfection Byproducts and Human Health ........................................................................ 5 2.3 Regulations ............................................................................................................................ 6

2.3.1 Safe Drinking Water Act ................................................................................................ 6 2.3.2 Disinfection Byproduct Regulations .............................................................................. 7 2.3.3 State and Local DBP Regulations .................................................................................. 7 2.3.4 Regulation Levels ........................................................................................................... 7 2.3.5 Compliance Dates ........................................................................................................... 8 2.3.6 Monitoring Requirements ............................................................................................... 9

2.4 Factors Affecting Disinfection Byproduct Formation ........................................................ 10 2.4.1 Organic Matter .............................................................................................................. 10 2.4.3 Disinfectant Type and Concentration ........................................................................... 11 2.4.4 Contact Time ................................................................................................................ 12 2.4.5 Temperature .................................................................................................................. 12 2.4.6 pH ................................................................................................................................. 12

2.5 Dartmouth Water Treatment Facilities ................................................................................ 12 2.5.1 Treatment Plant Layout ................................................................................................ 13

2.6 Trihalomethane Levels in Dartmouth MA .......................................................................... 18 2.7 Summary ............................................................................................................................. 20

3.0 Methodology ........................................................................................................................... 21 3.1 Water Characteristics .......................................................................................................... 21

3.1.1 Sample Collection......................................................................................................... 21 3.1.2 Sample Analysis ........................................................................................................... 22

3.2 Filtration .............................................................................................................................. 22 3.2.1 Filter Design ................................................................................................................. 22 3.2.2 Flow Rate ...................................................................................................................... 24 3.2.3 Filter Media .................................................................................................................. 25 3.2.4 Chemicals Used in Filtration Process ........................................................................... 25 3.2.5 Experiment Conditions ................................................................................................. 26

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3.2.6 Filtration Run ................................................................................................................ 27 3.3 Analytical Methods ............................................................................................................. 28

3.3.1 Sodium Hypochlorite .................................................................................................... 28 3.3.2 Polymer ......................................................................................................................... 30 3.3.3 Sodium Hydroxide ........................................................................................................ 31 3.3.4 Aluminum Sulfate......................................................................................................... 32 3.3.5 pH ................................................................................................................................. 32 3.3.6 Temperature .................................................................................................................. 32 3.3.7 Organic Carbon............................................................................................................. 33 3.3.7 UV254 ............................................................................................................................ 34 4.3.5 Specific UV Absorbance .............................................................................................. 34 3.3.8 Iron and Manganese ...................................................................................................... 35

4.0 Results and Analysis ............................................................................................................... 36 4.1 THM Reduction Alternatives .............................................................................................. 37

4.1.1 Change the Water Source ............................................................................................. 37 4.1.2 THM Removal after Filtration ...................................................................................... 37 4.1.3 Remove THM Precursors ............................................................................................. 37

4.2 Organic Carbon Measurements ........................................................................................... 38 4.2.1 TOC/DOC Data from Wells ......................................................................................... 38 4.2.2 TOC/DOC Data from Distribution System .................................................................. 39 4.2.3 TOC Data from Town of Dartmouth ............................................................................ 39

4.3 Bench Scale Filtration Results and Analysis....................................................................... 40 4.3.1 Iron and Manganese ...................................................................................................... 40 4.3.2 Organic Carbon............................................................................................................. 41 4.3.3 pH ................................................................................................................................. 43 4.3.4 Chlorine Residual ......................................................................................................... 43 4.3.5 UV254 Absorbance ........................................................................................................ 44 4.3.6 SUVA ........................................................................................................................... 45

4.4 Final Experiment for Organic Carbon Removal ................................................................. 46 4.4.1 Media ............................................................................................................................ 46 4.4.2 Chlorine Residual ......................................................................................................... 46 4.4.3 Polymer ......................................................................................................................... 47 4.4.4 pH ................................................................................................................................. 47 4.4.5 Results .......................................................................................................................... 47 4.4.6 Cost Analysis ................................................................................................................ 48

5.0 Conclusions and Recommendations ....................................................................................... 50 5.1 Conclusions ......................................................................................................................... 50 5.2 Recommendations for Moving Forward ............................................................................. 51

References ..................................................................................................................................... 52 Appendix A: Results of Well Water Characteristics .................................................................... 55

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Appendix B: Results of Distribution System Water Characteristics ............................................ 57 Appendix C: Iron and Manganese Results of Experiments .......................................................... 58 Appendix D: TOC/DOC Results of Experiments ......................................................................... 59 Appendix E: pH Results of Experiments ...................................................................................... 60 Appendix F: Chlorine Residual Results of Experiments .............................................................. 61 Appendix G: UV Results of Experiments ..................................................................................... 62 Appendix H: Final Experiment Results ........................................................................................ 63 Appendix I: Final Experiment Cost Analysis ............................................................................... 64

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List of Figures

Figure 1: Dartmouth Wall Map (Dartmouth Water Division, 2012) ............................................ 14 Figure 2: 579 Old Westport Road Treatment Plant ...................................................................... 14 Figure 3: 299 Chase Road Treatment Plant .................................................................................. 15 Figure 4: 687 Chase Road Treatment Plant .................................................................................. 15 Figure 5: Reed Road Map ............................................................................................................. 19 Figure 6: Assembled Bench Scale Filter Design .......................................................................... 23 Figure 7: Components of Bench Scale Filter ................................................................................ 23 Figure 8: Operation of Bench Scale Filter .................................................................................... 24 Figure 9: TOC Removal in Bench Scale Experiments ................................................................. 42 Figure 10: DOC Removal in Bench Scale Experiments ............................................................... 42 Figure 11: UV Absorbance throughout Filter ............................................................................... 45

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List of Tables Table 1: Chemical Structures of Regulated THMs ......................................................................... 3 Table 2: Chemical Structures of Regulated HAAs ......................................................................... 4 Table 3: Disinfection Byproducts regulated by the U.S. EPA and their Potential Health Effects

from Long-Term Exposure (adapted from U.S. EPA 2013b) .......................................... 5 Table 4: DBP Regulatory Limits Set by the U.S. EPA (adapted from U.S. EPA, 2010) ............... 8 Table 5: MRDLs and MRDLGs Set by the U.S. EPA (adapted from U.S. EPA 2010) ................. 8 Table 6: Monitoring Requirements for Stage 2 DBPR Compliance (adapted from MassDEP,

2009) ................................................................................................................................ 9 Table 7: Monitoring Criteria for TTHM and HAA5 (adapted from MassDEP, 2009)................. 10 Table 8: Town of Dartmouth Water Treatment Plants ................................................................. 13 Table 9: Sodium Hypochlorite Dosing in August 2013................................................................ 16 Table 10: Town of Dartmouth Filtration Design Parameters ....................................................... 18 Table 11: Town of Dartmouth, MA Reported THM Levels (µg/L) ............................................. 19 Table 12: Water Quality Sampling Locations .............................................................................. 21 Table 13: Water Quality Testing Parameters ................................................................................ 22 Table 14: Dartmouth Water Treatment Plant Chemical Dosing ................................................... 26 Table 15: Chemical Dosing and Media Configuration for Bench Scale Experiments ................. 27 Table 16: Parameters Tested in Bench scale Experiments ........................................................... 28 Table 17: Total THM Levels (µg/L) Reported to MassDEP ........................................................ 36 Table 18: Historical THM Data Provided by the Dartmouth Water Division .............................. 36 Table 19: TOC and DOC (mg/L) in Dartmouth Wells ................................................................. 38 Table 20: TOC and DOC (mg/L) in Dartmouth, MA ................................................................... 39 Table 21: TOC in Wells, Treatment Plant and Distribution System Reported to MassDEP ....... 40 Table 22: Iron Reduction (mg/L) through Bench Scale Filtration ................................................ 41 Table 23: Manganese Reduction (mg/L) through Bench Scale Filtration .................................... 41 Table 24: TOC and DOC Removal of Altered Chlorine Residual Experiments .......................... 44 Table 25: UV254 Reduction through Bench Scale Filtration ......................................................... 44 Table 26: SUVA Results from Experiments ................................................................................. 45 Table 27: Selected Conditions for Organic Carbon Removal ...................................................... 46 Table 28: Final Experiment Results .............................................................................................. 48 Table 29: 579 Old Westport Treatment Plant Filter Media Cost .................................................. 48 Table 30: Annual Cost of Dartmouth Conditions and Final Experiment Conditions ................... 49 Table 31: Filter Media Cost (obtained from Owen, 2014) ........................................................... 64

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Acronyms AWWA American Water Works Association CMR Code of Massachusetts Regulations DBP Disinfection Byproduct DBPR Disinfectant and Disinfection Byproduct Rule DOC Dissolved Organic Carbon GWS Groundwater System HAA Haloacetic Acids HAA5 5 regulated HAAs by the U.S. EPA HAN Halogenated Acetonitriles IDSE Initial Distribution System Evaluation LRAA Locational Running Annual Average MassDEP Massachusetts Department of Environmental Protection MCL Maximum Contaminant Level MCLG Maximum Contaminant Level Goal MGD Million Gallons per Day MRDL Maximum Residual Disinfectant Level MRDLG Maximum Residual Disinfectant Level Goal NOM Natural Organic Matter SDWA Safe Drinking Water Act SSS System Specific Study SUVA Specific Ultraviolet Absorbance THM Trihalomethanes TOC Total Organic Carbon TOX Total Organic Halogen TTHM Total Trihalomethanes (4 regulated THMs by the U.S. EPA) U.S. EPA United States Environmental Protection Agency UV Ultraviolet VSS Very Small System WTP Water Treatment Plant

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1.0 Introduction Disinfection byproducts (DBPs) are caused by the reaction of chlorine and natural organic matter (NOM) during the disinfection of drinking water to deactivate bacteria and pathogens. Total organic carbon (TOC) and dissolved organic carbon (DOC) concentrations are good predictors for the amount of DBPs that can be formed because a higher concentration of NOM in water will form more DBPs when chlorine is added to the water. Other factors affecting DBP formation include type and concentration of disinfectant, disinfectant contact time, temperature, and pH. It is suspected that some DBPs are carcinogenic and cause other negative health effects. There are 500 known DBPs; four compounds or groups of compounds are regulated by the U.S. Environmental Protection Agency (U.S. EPA), including total trihalomethanes (TTHMs), haloacetic acid (HAAs), bromate, and chlorite. The Town of Dartmouth drinking water treatment facilities use a Greensand filtration system to treat approximately 6.54 million gallons per day (MGD) of water which is distributed to approximately 23,400 customers. There are 13 groundwater wells, which are maintained by the Town of Dartmouth and treated in three water treatment facilities. The water is first dosed with sodium hypochlorite as a disinfectant. Then, a polymer is added and the pH is adjusted with sodium hydroxide before passing through the filter. The filters are designed to remove iron and manganese for aesthetics. The Dartmouth Treatment Plant is monitored under drinking water regulations set in place by the U.S. EPA and adopted by the Massachusetts Department of Environmental Protection (MassDEP). There are minimum chlorine residual levels, in addition to maximum trihalomethanes (THM) levels enforced by the MassDEP. In 2013, the Town of Dartmouth found high THM levels in water coming from the 579 Old Westport Road Facility.

The goal of this project was to optimize THM precursor removal at the 579 Old Westport Road facility while maintaining adequate iron and manganese removal. First, water samples from 13 groundwater wells and nine distribution system locations in Dartmouth were analyzed for TOC and DOC. Second, a bench scale filter was designed to mimic the conditions at the Dartmouth Treatment Plant, specifically the 579 Old Westport Road treatment location. Experiments were conducted by varying filter media, polymer, alum, sodium hydroxide, and sodium hypochlorite to determine the effectiveness of TOC, DOC, iron, and manganese removal. The following chapters provide background information on DBPs in drinking water, DBPs and human health, regulations, the factors affecting DBP formation, the Dartmouth Water Treatment Facilities, and THM levels in Dartmouth. Finally, the test methods and results are presented, followed by treatment recommendations for reducing THM levels in the Dartmouth Treatment Plant.

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2.0 Background Prior to experimentation and design, several topics were researched in order to address DBP control in drinking water. The following sections provide an overview of DBPs in drinking water, the effect DBPs have on human health, regulations that limit DBP concentrations, and the factors affecting the formation of DBPs. Lastly, information on the Town of Dartmouth Water Treatment Plants is provided.

2.1 Disinfection Byproducts in Drinking Water Disinfection is used to inactivate potentially harmful microorganisms in drinking water to protect human health. Although drinking water disinfection has been shown to be the most effective way to inactivate bacteria and pathogens, concerns were raised in 1974 when Dutch chemist Johannes J. Rook discovered that chlorine and bromide react with organic matter to create DBPs, more specifically, chloroform (Centers for Disease Control and Prevention, 2013). Since then, other DBPs have been discovered such as THMs, haloacetic acids (HAAs), bromate and chlorite. DBPs are chemical compounds that form when disinfectants react with NOM in the water. NOM originates from living organisms. After plants and animals die, their matter is decomposed into compounds still containing carbon and can enter waters (Bhardwaj, 2006). This matter can be present as humic acids, fulvic acids, intermediate organic fractions, colloidal suspensions, organic acids, and carbon functional groups. Typically, the organic matter exists in the water as humic acid or fulvic acid. Since NOM is primarily made up of carbon, it is often quantified as the concentration of TOC and DOC. 2.1.1 Types of Disinfection Byproducts There are about 500 known DBPs, though not much is known about most of them (Richardson, 2003). DBPs that are regulated by the U.S. EPA include THMs, HAAs, bromate and chlorite. Other known DBPs include aldehydes, haloacetonitriles, haloketones, haloaldehydes, chloropicrin, cyanogens chloride, and cholorophenols (Bhardwaj, 2006). DBPs can be classified as halogenated or non-halogenated. Halogenated DBPs are formed when the NOM combines with halogens such as chlorine or bromide. Non-halogenated DBPs include aldehydes, ketones, and carboxylic acids (Richardson, 2003). The majority of DBPs formed in a water treatment plant are THMs and HAAs, both of which are halogenated. DBPs can be formed from chemical disinfectants (chlorine, chloramines, chlorine dioxide). Tables 1 and 2 show the regulated THMs and HAAs, respectively.

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2.1.1.1 Trihalomethanes THMs form when organic and inorganic matter in the water reacts with chlorine or chloramines. As shown in Table 1, each THM contains a carbon atom at the center, which is bonded to one hydrogen atom and three halogen atoms around the carbon. The halogens may consist of chlorine (Cl) from the disinfectant or bromine (Br) from naturally occurring bromide (Br-) in the water. The four regulated THMs are chloroform, bromodichloromethane, dibromochloromethane and bromoform (Bull, 2009). The sum of these four regulated THMs is called total trihalomethanes (TTHMs). There are also many iodinated forms of THMs that are not regulated (U.S. EPA, 2013a).

Table 1: Chemical Structures of Regulated THMs

Name Chemical Formula Structural Formula

Chloroform CHCl3

Bromodichloromethane

CHCl2Br

Dibromochloromethane CHClBr2

Bromoform CHBr3

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2.1.1.2 Haloacetic Acids There are nine HAAs total, but only five are regulated. Regulated HAAs include chloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid, and dibromoacetic acid. These are collectively known as HAA5. Like THMs, they form when organic or inorganic matter present in the water reacts with chlorine or chloramines. As shown in Table 2, each HAA contains a carboxyl group (one carbon, two oxygen, and one hydrogen, COOH). The carbon in the carboxyl group is bonded to an additional carbon, which is bonded to three other molecules. These three molecules are a combination of the elements hydrogen and chlorine, or hydrogen and bromine (U.S. EPA, 2013a).

Table 2: Chemical Structures of Regulated HAAs

Name Chemical Formula Structural Formula

Chloroacetic acid ClCH2COOH

Dichloroacetic acid CHCl2COOH

Trichloroacetic acid C2HCl3O2

Bromoacetic acid BrCH2COOH

Dibromoacetic acid Br2CHCOOH

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2.1.1.3 Bromate Bromate (BrO3-) forms when bromide (bromine anion, Br-) reacts with ozone (O3) that has been used for disinfection. Bromide can naturally exist in raw water from sources such as bromide salts or agricultural chemicals (U.S. EPA, 2006). 2.1.1.4 Chlorite and Chlorate Chlorite (ClO2-) and chlorate (ClO3-) can be formed when chlorine dioxide (ClO2) or chlorine reacts in the water as it travels through the water system (U.S. EPA, 2006). If sodium hypochlorite solution, NaOCl, is used in the disinfection process, chlorite and chlorate ions can also be formed as the solution decomposes. The majority of the ions formed are typically chlorite, and therefore, the U.S. EPA only regulates chlorite (Grant-Trusdale, 2005). 2.1.1.5 Other Disinfection Byproducts Many other DBPs exist but are not typically found at levels comparable to THMs and HAAs. Aldehydes (primarily formaldehyde, HCHO, and acetaldehyde, CH3CHO), haloketones, ketoacids, carboxylic acids are all DBPs that are formed when the disinfectant ozone is used. If chlorine based disinfectants are also used, other aldehydes may form (i.e. trihaloacetaldehydes). Another DBP is MX, 3-chloro-4(dichloromethyl)-5-hydroxy-2(5H) furanone, which is a mutagen that forms when humic acid and chlorine react with each other (Wright, 2002).

2.2 Disinfection Byproducts and Human Health In 1976, the National Cancer Institute published results that linked chlorinated water consumption with bladder cancer in laboratory animal testing (Richardson et al., 2002). This was the first of several reports to show a positive correlation between chronic DBP exposure and cancer. The U.S. EPA first regulated DBPs in 1979 due to their health risks to humans and animals (See Section 2.3) (Richardson et al., 2002). Table 3 shows the DBP groups regulated by the U.S. EPA and their potential health effects from long-term exposure (U.S. EPA, 2013b).

Table 3: Disinfection Byproducts regulated by the U.S. EPA and their Potential Health Effects from Long-Term Exposure (adapted from U.S. EPA 2013b)

Contaminant Potential Health Effects

Bromate Increased risk of cancer

Chlorite Anemia, nervous system effects in children

Haloacetic acids (HAA5) Increased level of cancer

Total Trihalomethanes (TTHMs)

Complications with liver, kidney, or central nervous system, and increased risk of cancer

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Other epidemiological studies have also shown correlations between consistent consumption of water with high THMs and low birth weight, stillbirth, intrauterine growth retardation, and spontaneous abortion (Richardson et al., 2002). Swan and Waller (1998) ran a study on approximately 250 pregnant women who drank water with a high, but still U.S. EPA compliant concentration of THMs (>75 μg/L) and compared it to approximately 250 other women who drank water with a lower THM concentration (

sources such as groundwater and reservoirs; therefore it is important to protect water sources prior to treatment (U.S. EPA, 2013e). 2.3.2 Disinfection Byproduct Regulations DBPs, specifically TTHMs, were first regulated in 1979 at 0.1 mg/L for systems serving over 10,000 people (U.S.EPA, 2013d). This regulation was then revised and modified as part of the 1996 SDWA amendments and included The Stage 1 Disinfectants and Disinfection Byproduct Rule (DBPR), where TTHM limits were lowered to 0.08 mg/L (U.S. EPA, 1998). The Stage 1 DBPR also regulated HAAs, chlorite, and bromate; set Maximum Contaminant Limit Goals (MCLGs); and applied to all community and non-transient non-community water systems using chemical disinfectants (U.S. EPA, 1998). MCLGs are “non-enforceable health goals, based solely on possible health risks and exposure over a lifetime, with an adequate margin of safety” (U.S. EPA, 2013a). The Stage 2 DBPR was proposed in August of 2003 and completed on December 15, 2005. The Stage 2 Rule set additional MCLGs and is applicable to all water systems that use a disinfectant other than ultraviolet (UV) light (U.S. EPA, 2005). 2.3.3 State and Local DBP Regulations State and local governments are required to comply with the U.S. EPA SDWA, but are also able to enforce stricter limits. To ensure safety in Massachusetts, the MassDEP adopts all federal drinking water standards as outlined in the Code of Massachusetts Regulations (CMR) Chapter 310 Section 22.07E. Rule 22.07E, called “Disinfection Byproducts, Disinfectant Residuals and Disinfection Byproduct Precursors,” is applicable to both community water systems and non-transient non-community water systems, which add a chemical disinfectant at any point in the drinking water treatment process (MassDEP, 2009). 2.3.4 Regulation Levels The maximum levels of allowable DBPs are regulated as Maximum Contaminant Levels (MCLs). The MCL aims to be as close to the MCLG as possible. THMs and HAAs typically occur at higher levels than other known and unknown DBPs. Thus, a reduction in THMs and HAAs may indicate a reduction in other DBPs (U.S. EPA, 2005). Public water systems are required to comply with the limits as shown in Table 4. Compliance with MCLs in the Stage 2 DBPR is based on annual averages computed quarterly known as Locational Running Annual Average (LRAA). The LRAA is the average DBP level at a given sampling location based on four quarterly samples taken over a 12 month period. The requirements that must be reported include the number of samples taken during the quarter; the location, date and results of the last quarter; the arithmetic average taken in that quarter; and whether or not the MCL was violated (MassDEP, 2009). If the LRAA for any consecutive four quarters is greater than the maximum

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TTHM and/or HAA5 levels, the supplier is in violation and must notify the public pursuant as well as the Department pursuant (MassDEP, 2009).

Table 4: DBP Regulatory Limits Set by the U.S. EPA (adapted from U.S. EPA, 2010)

DBP Stage 2 DBPR

MCLG (mg/L) MCL (mg/L)

THM

Bromodichloromethane Zero - Bromoform Zero -

Dibromocloromethane 0.06 - Chloroform 0.07 -

Total - 0.08

HAA

Dichloroacetic acid Zero - Trichloroacetic acid 0.02 - Chloroacetic acid 0.07 - Bromoacetic acid - -

Dibromoacetic acid - - Total - 0.06

Bromate Zero 0.01 Chlorite 0.8 1.0

The U.S. EPA also regulates disinfectants based on the maximum residual disinfectant levels (MRDL) as shown in Table 5. The MRDL applies to community water systems and non-transient non-community water systems that use a chemical as a disinfectant at any point from the source to the final distribution point. The U.S. EPA also sets a maximum residual disinfectant level goal (MRDLG). Similar to the MCLs and MCLGs for DBPs, public water systems are required to comply with the disinfectant concentration limits. However, at any point necessary for public safety, such as in the case of a microbiological contamination problem, systems that use only chlorine or chloramines may increase residual disinfectant levels (MassDEP, 2009).

Table 5: MRDLs and MRDLGs Set by the U.S. EPA (adapted from U.S. EPA 2010)

Regulated Disinfectants

Stage 2 DBPR

MRDL (mg/L) MRDLG (mg/L) Chlorine 4.0 as Cl2 4.0

Chloramines 4.0 as Cl2 4.0 Chlorine Dioxide 0.8 0.8

2.3.5 Compliance Dates The Stage 2 DBPR requires monitoring to ensure public water systems are in compliance with regulatory limits. “The supplier of water must use an Initial Distribution System Evaluation

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(IDSE) to determine locations with representative high TTHM and HAA5 concentrations throughout their distribution system” (MassDEP, 2009). The IDSE is a one-time evaluation, from which public water systems will chose one of four options to proceed. These options include (1) qualifying for a very small system waiver, (2) meeting 40/30 certification requirements, (3) conducting a system specific study or (4) conducting standard monitoring (U.S. EPA, 2006). These options are defined in Table 6.

Table 6: Monitoring Requirements for Stage 2 DBPR Compliance (adapted from MassDEP, 2009)

Monitoring Option

System Requirements Further IDSE Requirement

Very Small System Waiver (VSS)

Serving fewer than 500 people None

TTHM and HAA5 data

40/30 Certification TTHM < 0.040 mg/L and HAA5 < 0.030

mg/L during a 2-year period Submit 40/30 Certification No Stage 2 DBPR monitoring violations

System Specific Study (SSS)

Meet IDSE requirements using existing monitoring results or a distribution

systems hydraulic model

Prepare SSS plan and IDSE report

Standard Monitoring

Any system

One year of distribution system monitoring at

multiple locations Prepare a standard

monitoring plan and a IDSE report

Submissions of IDSE monitoring plans, SSS plans and 40/30 certifications for different types of public water systems started on October 2006 and continued until April of 2008. Following this step, the completion and submission of the IDSE reports were done from September 2008 to July 2010. Finally, the compliance monitoring started on April 2012 and was completed on October 2013. 2.3.6 Monitoring Requirements The U.S. EPA and MassDEP also have monitoring requirements for TTHM samples. All samples must be taken during normal operating conditions. Suppliers who qualify for reduced monitoring must obtain approval by the MassDEP for sampling. All TTHM and HAA5 samples must be collected at the same frequency for all monitoring locations (MassDEP, 2009). Monitoring frequency requirements based on system type are shown in Table 7.

9

Table 7: Monitoring Criteria for TTHM and HAA5 (adapted from MassDEP, 2009)

Type of System

Number of People Served

Minimum monitoring frequency

Sample location in the distribution system Exceptions

Systems using surface

water/ground water under

direct influence of

surface water

≥ 10,000 Four per quarter

Minimum 25% of samples at locations representing

maximum residence time None

Remaining samples taken at locations representative of at least average residence time

500 to 9,999

One per quarter

Locations representing maximum residence time

None

< 500 One per year in August

Locations representing maximum residence time

If sample is taken one per quarter, take at a point reflecting the maximum residence

time Systems using only ground

water not under direct influence of

surface water, system uses a

chemical disinfectant

≥ 10,000 One per quarter

Locations representing maximum residence time

None

< 10,000 One per year in August

Locations representing maximum residence time

If sample exceeds MCL, increase

monitoring to one per quarter, taken at a point reflecting the maximum residence

time For a plant to qualify for reduced monitoring for TTHMs and HAA5s, systems must take monthly TOC samples every thirty days at a specific location before any treatment occurs. The TOC LRAA of the source water must be less than or equal to 4.0 mg/L. Once qualified, a system may reduce TOC monitoring to quarterly samples (MassDEP, 2009).

2.4 Factors Affecting Disinfection Byproduct Formation There are many factors that affect DBP formation, including organic matter concentration, type and concentration of disinfectant, disinfectant contact time, temperature and pH. These factors are discussed in the following sections. 2.4.1 Organic Matter NOM present in water is a precursor for DBPs. NOM is composed of approximately 50 carbon, 35 percent oxygen, 5 percent hydrogen, 3 percent nitrogen and low amounts of phosphorous,

10

sulfur and trace metals (Westerhoff, 2006). Therefore TOC and DOC concentrations are good predictors for the amount of DBPs that can be formed. Generally, a higher concentration of TOC in water will form more DBPs when chlorine is added to the water. Therefore, removing precursors prior to the addition of disinfectants can control the formation of DBPs (U.S. EPA, 2006). Organic precursors can be removed through processes such as coagulation and sedimentation, or activated carbon (Droste, 1997). The nature of organic matter is also a factor is DBP formation (Bull, 2009). As discussed in Section 2.1, NOM is primarily composed of humic and fulvic acids. Humic acids are more likely to form a greater amount of TTHMs and HAA5 because they have a higher TOC concentration. Fulvic acid has a lower TOC level and therefore forms less TTHM and HAA5 (Gnagy, 2012). 2.4.3 Disinfectant Type and Concentration Disinfectants used in water treatment include chlorine, chloramines, chlorine dioxide, UV, and ozone. Chlorine has been found to pose the highest risk of DBP formation, followed by chloramines, chlorine dioxide, and finally ozone (Droste, 1997). Chlorine is commonly used in the U.S. as it is the most cost effective primary disinfectant in comparison to others. Chloramines are often applied in secondary disinfection for their stability in distribution systems (Bull, 2009). The type of disinfectant used affects whether halogenated or non-halogenated DBPs will form. Halogenated DBPs, such as THMs, are more common and are often associated with the use of hypochlorite and chlorine gas for disinfection (Bull, 2009). The formation of these DBPs can occur when the water is in either the treatment plant or distribution system. When organic and inorganic compounds react with free chlorine, free bromine, or free iodide, halogenated DBPs are formed (U.S. EPA, 2006). When chlorine is used as a disinfectant, about 50 percent of the total organic halogen (TOX) can be attributed to known DBPs such as THMs, HAAs and halogenated acetonitriles (HAN), while the other 50 percent is unknown. For other disinfectants, only about 10% of TOX is attributed to identifiable DBPs. Using a combination of disinfection methods can complicate the prediction of DBP formation. The manner in which disinfectants are applied is also a factor. For example, if pre-formed chloramines are used, this could eliminate any contact time between free chlorine and organic matter, which may reduce the potential for DBP formation (Bull, 2009). According to Doesderer et al. (2013), high concentrations of disinfectants lead to higher levels of DBPs. In water treatment plants, disinfection can be applied prior to or after other treatment processes. Because pre-chlorination uses higher doses, elimination of pre-chlorination can reduce DBP formation. An alternate disinfectant such as UV could be utilized instead because the DBPs formed by UV disinfection are insignificant (Droste, 1997).

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2.4.4 Contact Time Higher contact time increases the risk of DBP formation. Most water treatment plants have 30 to 120 minutes of contact time with chlorine before entering the distribution system. Water remains in the distribution system anywhere from several hours to several days as it moves to individual households, most typically 1 to 3 days (Westerhoff, 2006). In general, higher concentrations of THMs accumulate in the water as time goes by. However, HAAs are known to biodegrade over time when the disinfectant residual is low. Thus, HAA concentrations are more likely to be lowest in the area of the distribution system where the disinfectant residuals are expended (U.S. EPA, 2006). 2.4.5 Temperature Temperature often correlates with DBP levels. Higher temperatures allow bacteria and other organisms to thrive, which result in higher NOM concentrations in warmer weather. Since DBPs are formed by the reaction between NOM and chlorine, more DBPs are formed. High temperatures also serve as catalysts, causing reactions to take place quicker (Doesderer et al., 2013). For example, at a normal summertime temperature of 25˚C, the concentration of THMs is almost twice that measured at 10˚C for a 24-hour contact period (Westerhoff, 2006). However, during these warmer months, the demand for water is higher, therefore decreasing the residence time of the water in the distribution system. In warm months with low demand, the THMs are typically highest (U.S. EPA, 2006). 2.4.6 pH With an increased pH, a higher number of THMs are formed. However, with an increasing pH, the opposite occurs for HAAs; the amount formed decreases (Doesderer et. al., 2013). The most likely cause for an increase in THMs is due to an increased rate of hydrolysis, which breaks down aromatic bonds. This allows for more halogenated matter and thus more THMs to form (Brown et. al., 2011). HAA precursors are sensitive to base hydrolysis. Therefore, pH can lower their formation pathways resulting in a decrease of HAAs (U.S. EPA, 2006).

2.5 Dartmouth Water Treatment Facilities The public water system in the Town of Dartmouth, Massachusetts serves approximately 23,400 customers and is operated by the Dartmouth Water and Sewer Division (Sullivan, 2013). Water is sourced from 13 groundwater wells maintained by the Town of Dartmouth and is treated in three water treatment facilities. Information about each facility is shown in Table 8.

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Table 8: Town of Dartmouth Water Treatment Plants

Treatment Plant Year Built Capacity 1

(MGD) Source Wells

579 Old Westport Road 2003 1.97

Violetta 1, Violetta 2, Violetta 3, Pinelli 1, Pinelli 2

299 Chase Road 1999 2.34 F1, F2, A, B, C

687 Chase Road 1992 2.23 E1, E2, D

1 Capacity of each treatment plant is based on the combined capacity from treatment plant source wells (Dartmouth Water Division, 2012) The town also purchases pre-treated water from April to September from the City of New Bedford, Massachusetts to handle peak demand in the summer months (Sullivan, 2013). New Bedford treats water at the Quittacass Water Treatment Plant, where it is sourced from five ponds. New Bedford treatment consists of filtration, disinfection with chloramines, corrosion control, and fluoridation. This water is brought to the Dartmouth Faunce Corner Pump Station located in North Dartmouth and pumped into the system at a maximum rate of 4,000 gallons per minute (5.76 MGD) (Dartmouth Water Division, 2012). 2.5.1 Treatment Plant Layout Each of the three treatment plants in the Town of Dartmouth obtain water from multiple wells that are combined before treatment. Treatment consists of pre-chlorination, filtration, post- chlorination and pH adjustment. Figure 1 shows the location of the treatment plants, wells, and storage tanks for the Dartmouth Water Department. Schematics of the plants are shown in Figure 2, Figure 3 and Figure 4. Details on each process are provided in the following sections.

13

Figure 1: Dartmouth Wall Map (Dartmouth Water Division, 2012)

Figure 2: 579 Old Westport Road Treatment Plant

14

Figure 3: 299 Chase Road Treatment Plant

Figure 4: 687 Chase Road Treatment Plant

15

2.5.1.1 Pre-chlorination Each treatment facility in Dartmouth chlorinates the drinking water with sodium hypochlorite (NaOCl). Chlorination is used to inactivate potential harmful microorganisms such as bacteria, protozoa and viruses. Sodium hypochlorite dissociates in water to form hypochlorite ion (OCl-) as shown in Reaction 1.

𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 + 𝐻𝐻2𝑁𝑁 → 𝑁𝑁𝑁𝑁 + 𝑁𝑁𝑁𝑁𝑁𝑁− (Reaction 1) Chlorine can then exist in two forms in water, hypochlorous acid and hypochlorite ion as shown in Reaction 2. This reaction is pH dependent. A pH of less than about 7.5 will favor the formation of HOCl. Hypochlorous acid is a better disinfectant than the hypochlorite ion which is dominant at a pH of greater than 7.5 (Hach Company, 2013). Hypochlorous acid in water inactivates harmful microorganisms by oxidizing the cell wall (Myers, 2007).

𝑁𝑁𝑁𝑁𝑁𝑁− + 𝐻𝐻2𝑁𝑁 ↔ 𝐻𝐻𝑁𝑁𝑁𝑁𝑁𝑁 + 𝑁𝑁𝑁𝑁𝑁𝑁𝐻𝐻− (Reaction 2) The Town of Dartmouth abides by all U.S. EPA regulations and the groundwater 310 CMR DEP Drinking Water Regulations on disinfection standards. This regulation states that groundwater systems (GWS) “that use chemical disinfection and serve more than 3,300 people must continuously monitor their disinfectant concentration. GWSs must maintain the minimum disinfectant residual concentration determined by the state” (U.S. EPA, 2010). In the state of Massachusetts, the residual disinfectant concentration must be greater than 0.2 mg/L. The concentration is noted daily in the monthly compliance report sent to the MassDEP. Data on sodium hypochlorite dosing and residuals at each of the three treatment plants is shown in Table 9. The pre-chlorination dose at the Dartmouth Treatment Plants target a residual of 0.4 mg/L measured immediately after filtration. This is achieved through the addition of sodium hypochlorite. Additional sodium hypochlorite is then added after filtration to maintain a residual in the distribution system.

Table 9: Sodium Hypochlorite Dosing in August 2013

Treatment Plant Average Chemical Dosage1

(mg/L) Average Residual2

(mg/L)

579 Old Westport Road 3.08 1.01

299 Chase Road 4.69 1.27

687 Chase Road 3.43 1.20 1 Total chemical dosage including pre and post chlorination 2 Residual is measured at 100 foot sample tap downstream of treatment plant as Cl2

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2.5.1.2 Pre-treatment pH Adjustment Before filtration through Greensand media and after the pre-filtration dose of sodium hypochlorite and polymer, sodium hydroxide is used to raise the pH of the water to about 8.1-8.2. This helps to maintain the effectiveness of the Greensand media. 2.5.1.3 Filtration After pre-chlorination, pre-treated water at all three Dartmouth plants is filtered. The filtration process removes suspended particles in the water as it passes through the filter media. There are several different types of media that can be used for water filtration. The Dartmouth Water Division uses Greensand and GreensandPlus media. In addition to removing particles, Greensand removes iron and manganese from the water, which are naturally present in the raw well water. The U.S. EPA gives secondary standards for iron and manganese that are non-enforceable but recommended for aesthetics. Greensand is a clay mineral that comes from glauconite, a sedimentary rock that typically has a green color. The glauconite is mined, washed, screened, and treated with chemicals. The media coating of the Greensand and GreensandPlus contains manganese dioxide, which reacts with and removes both iron and manganese. Greensand filters have a glauconite core with an ionic bond to the manganese dioxide coating. The GreensandPlus media removes hydrogen sulfide in addition to iron and manganese. This media is made of silica sand, and the manganese dioxide coating is fused to the core instead of having an ionic bond. The GreensandPlus lasts longer than Greensand due to its ability to better endure operation conditions. It can also perform at higher temperatures and pressures (Carbon Enterprises Inc., 2013). The pH may have an effect on how well the filter performs. A pH lower than 6.8 and higher than 8.5 may not properly remove iron and manganese (Seeling et al., 1992). Since particles accumulate over time in the filters, they must be backwashed to remove the particles. Backwashing is when the flow of water is reversed at a higher velocity to dislodge particles. The Town of Dartmouth backwashes filters based on flow, pressure differential and iron and manganese testing post filtration. After a service cycle, the filters are backwashed and then recharged with a solution of potassium permanganate (KMnO4), restoring the oxidative capacity of the Greensand (Carbon Enterprises Inc., 2013). In addition to Greensand, the filters contain layers of anthracite and gravel. The 579 Old Westport Road plant uses filter media containing 18 inches of anthracite, 18 inches of manganese Greensand, and finally a 16 inch graded gravel bed. A polymer coagulant, Kroff CR-1650, to aid in the reduction of high TOC levels associated with the Violetta wells is also used at the 579 Old Westport Road Treatment Plant. Thus, the filters are intended to remove particles, iron, manganese and TOC. Operation data for each of the filtration systems is provided in Table 10.

17

Table 10: Town of Dartmouth Filtration Design Parameters

Treatment Plant

Number of

Filters

Filter Size (ft2) Media

Flow Rate

(MGD) Coagulant Backwash Frequency

579 Old Westport Road

Six 62.6 Greensand 1.9 Kroff CR-

1650 Daily

299 Chase Road Four -

1 Greensand 1.2 None Weekly

687 Chase Road Four -

1 2 Greensand,

2 GreensandPlus 1.2 None Weekly

1Information not provided 2.5.1.4 Post-chlorination After filtration, the water is chlorinated again for secondary disinfection to maintain a residual. These levels range from 1.02 -1.60 mg/L (Rhuda, 2014). 2.5.1.5 Post-treatment pH Adjustment Though a pH below 7.5 can provide better disinfection properties, water at low pH can also be corrosive throughout the distribution system (AWWA, 2011). Thus, the Town of Dartmouth injects sodium hydroxide (NaOH) to the treated water before it leaves the plant in order to raise the pH. The pH is measured after the addition of sodium hydroxide and is maintained between 8.0 and 8.5. Corrosion control helps Dartmouth to remain in compliance with Rule 310 CMR 22.06B for lead and copper in drinking water, as lead and copper can leach into water from household plumbing if water is corrosive. Violation of this rule would mean that “10% of tap waters samples collected during any monitoring period” (MassDEP, 2009) had greater than 0.015 mg/L of lead or 1.3 mg/L of copper.

2.6 Trihalomethane Levels in Dartmouth MA The Town of Dartmouth monitors for DBPs per U.S. EPA and MassDEP regulations and is being proactive in identifying areas for improvement. The treatment plant monitors THMs as well as HAA5, on a quarterly basis at four locations in the distribution system: 965 Reed Road, 751 Allen Street, 354 Elm Street and 307 Smith Neck Road. Table 11 shows these results. Under the Stage 1 DBPR, the running annual average (RAA) is calculated as the average of TTHMs from the previous four quarters, including concentrations from all sampling locations. The MCL under this rule was 80 μg/L. Under the Stage 2 DBPR that was put into effect in January 4, 2006, the LRAA is more stringent. This rule requires water systems to meet the LRAA for TTHMs at each of four sampling locations individually. The MCL under the Stage 2 DBPR is still 80 μg/L.

18

Table 11: Town of Dartmouth, MA Reported THM Levels (µg/L)

Location November

2012 February

2013 May 2013

August 2013

November 2013

965 Reed Rd THM Level 90.5 83.5 76.2 95.5 48.1

LRAA 22.6 43.5 62.6 86.4 75.8

751 Allen St THM Level 73.0 63.8 76.7 74.8 84.6

LRAA 18.3 34.2 53.4 72.1 75.0

354 Elm St THM Level 53.1 35.9 47.2 74.1 66.2

LRAA 13.3 22.3 34.1 52.6 55.9

307 Smith Neck Rd

THM Level 56.5 49.7 39.7 66.2 68.8

LRAA 14.1 26.6 36.5 53.0 56.1 As shown in Table 11, the TTHM LRAA value at Reed Road in August 2013 was 86.3 μg/L. Thus, the third quarter value is in violation of the U.S. EPA MCLs (Dartmouth Water Division, 2013a). Water from the 965 Reed Road location is treated at the 579 Old Westport Road Plant. This plant consists of pre-chlorination, pH adjustment, iron and manganese removal through Greensand Filtration, and post-chlorination. Figure 5 shows that the pipes end at Reed Road with a 16-inch diameter pipe. At this location there is a low flow in the area. Since there are only approximately 300 customers, there is limited demand, which may contribute to the high levels of THMs in that area.

Figure 5: Reed Road Map

19

The Town of Dartmouth has attempted many different approaches to reduce THM levels. Per recommendations from a consultant in 2011, an automatic flushing device was installed in the distribution system along the northern end of Reed Road. This approach was unsuccessful. The Dartmouth plant has flushed the system numerous times; however TTHM levels still did not fall below the locational average limit and the flushing device was removed (Sullivan, 2013). In October 2013, the Town also implemented a Solar Bee mixing unit in the Cross Road Storage tank to eliminate stagnation, therefore providing a uniform water age and consuming less chlorine, which leads to the formation of DBPs (Dickinson, 2011). As shown in Table 11, the THM level at 965 Reed Road was 76.2 - 95.5 μg/L prior to October 2013, and 48.1 μg/L in November 2013. Therefore it appears (based on limited data) that the mixing unit had a positive effect on reducing THMs at this location. However, THM levels were in the 66.2 to 84.6 μg/L range at other locations in the distribution system in November. Therefore additional approaches to reduce THM levels are desired.

2.7 Summary Based on the THM levels reported by Dartmouth Water Division between November 2012 and November 2013, it is evident that action is necessary to keep Dartmouth in compliance with U.S. EPA and MassDEP regulations. The goal of this project was to develop solutions for THM reduction in the drinking water of Dartmouth, MA by focusing on improving their treatment process. Since THM formation is heavily dependent on organic matter and disinfectant concentration, this project focused on reduction of TOC and DOC while reducing initial disinfectant dose. A bench scale filtration column was designed to test different chemical doses and filtration media, in order to determine optimal TOC and DOC removal while maintaining iron and manganese removal. These methods are discussed in Section 3.

20

3.0 Methodology The following sections describe the methods used to measure TOC and DOC in the drinking water from the Town of Dartmouth and evaluate process modifications to reduce organic carbon, thus reducing the potential for formation of THMs. The following procedures describe water sampling, initial water quality analysis, and bench scale testing of filtration to remove organic matter. The data obtained were used to determine feasible options for the Town of Dartmouth to reduce the formation of THMs in their drinking water, while maintaining adequate iron and manganese removal.

3.1 Water Characteristics Samples from wells and the distribution system were collected and analyzed to determine characteristics of the raw and filtered water at the Dartmouth Treatment Plants. 3.1.1 Sample Collection Water samples were collected at 13 wells located on treatment plant property, and at nine distribution system locations throughout Dartmouth, MA. Distribution system sampling locations were chosen based on regularly sampled locations for DBP compliance at the Dartmouth Water Division. Sampling locations are listed in Table 12.

Table 12: Water Quality Sampling Locations

Sample Type Sample Location Well Dates Collected

Well

579 Old Westport Road Treatment Plant

Violetta 1, Violetta 2, Violetta 3, Pinelli 1,

Pinelli 2 September 11 October 11 January 23

299 Chase Road Treatment Plant

F1, F2, A, B, C

687 Chase Road Treatment Plant

E1, E2, D

Distribution System

285 Old Westport Road (U. Mass)

September 20 October 11

November 13

250 Faunce Corner Road (Wellness Center) 737 State Road (Best Western)

1228 Russells Mills Road (Davoll's) 397 Round Hill Road (Round Hill)

249 Russells Mills Road (Police Station) 732 Dartmouth Street (Library)

751 Allen Street (Pumping Station) 965 Reed Road (Harvey Industries)

21

3.1.2 Sample Analysis To determine conditions of the water prior to and after treatment, water samples were tested for temperature, pH and TOC/DOC. TOC and DOC are precursors for THMs, and the formation of THMs is further affected by pH and temperature. Parameters tested are listed in Table 13, and methods are described in Section 3.3.

Table 13: Water Quality Testing Parameters Parameter Instrument Standard Method Number

Temperature Traceable©

Thermometer 2550

pH Accumet AB15 pH Meter 4500-H+

Total and Dissolved Organic Carbon

Shimadzu TOC-5000

5310

3.2 Filtration The 579 Old Westport Road Treatment Plant uses pre-chlorination, coagulation with Kroff KR-C1650 polymer, filtration with Greensand media and anthracite coal, post-chlorination, and both pre and post pH adjustment. This plant was replicated because of its pattern of higher TOC/DOC levels than those found at the other plants. These processes were simulated at the bench scale. The following sections provide details on the bench scale filter design. 3.2.1 Filter Design In order to replicate the Dartmouth water treatment process, a bench scale column was designed and built, as shown in Figure 6. A clear acrylic column with a diameter of one inch and a height of 7.5 inches was chosen for the laboratory experiments based on building feasibility and available materials. To evenly disperse the water through the filter, stainless steel wire mesh was placed at the top of the filter, with a rubber ring to hold it in place. To hold the media in place, stainless steel wire mesh was also placed at the base of the filter. The filter unit was detachable at the top and bottom to enable the media to be changed and the column to be cleaned. Figure 7 shows the components of the filter.

22

Figure 6: Assembled Bench Scale Filter Design

Figure 7: Components of Bench Scale Filter

Figure 8 shows the filter setup during operation with the pump, filter, influent and effluent water. There is piping connected from the influent and to the pump, as well as from the pump to the filter and the filter to the effluent beaker placed on the lab bench. The filter was held vertically approximately 10 inches from the lab bench. The chemically treated influent water was held in a 20 L plastic carboy placed on the upper level of the lab bench.

7.5 inches

Wire Mesh Rubber Ring

Influent

Effluent

23

Figure 8: Operation of Bench Scale Filter

3.2.2 Flow Rate The 579 Old Westport Road Treatment Plant operates with a design flow rate of 250 gpm/filter, with a bed area of about 62.6 square feet per filter. Thus, the treatment plant filters operate with a hydraulic loading rate of about 4 gpm/ft2. This hydraulic loading rate was replicated in the bench scale column. The bench scale filtration flow rate was calculated using Equation 1, where Q is the loading rate (4 gpm/ft2) and A is the area:

Loading Rate = 𝑄𝑄𝐴𝐴

= 4 𝑔𝑔𝑔𝑔𝑔𝑔𝑓𝑓𝑓𝑓2

(Equation 1)

The area was calculated by using Equation 2, where D is the diameter of the filter (1 inch):

𝐴𝐴𝐴𝐴𝐴𝐴𝑁𝑁 = 𝜋𝜋 𝐷𝐷2

4 (Equation 2)

Rearranging Equation 1 to solve for Q and substituting in Equation 2 yields:

Filter

Influent

Effluent

Pump

Pump Controller

24

𝑄𝑄 =4 𝑔𝑔𝑔𝑔𝑔𝑔𝑓𝑓𝑓𝑓2

(𝜋𝜋 � 1 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓12 𝑖𝑖𝑖𝑖𝑖𝑖ℎ𝐴𝐴𝑒𝑒�

2

4 𝑔𝑔𝑔𝑔𝑔𝑔𝑓𝑓𝑓𝑓2

)

𝑄𝑄 = 0.022 𝑔𝑔𝑔𝑔𝑔𝑔 �3785.41 𝑔𝑔𝑚𝑚

1 𝑔𝑔𝑁𝑁𝑁𝑁� = 82.6

𝑔𝑔𝑚𝑚𝑔𝑔𝑖𝑖𝑖𝑖

Thus the bench scale flow rate was 82.6 mL/min. A running time of two hours was selected based on time constraints and feasibility of running multiple tests. This time was long enough to determine any breakthrough from the filter. The volume of water needed was calculated using Equation 3 where Q is the loading rate (82.6 mL/min), V is the volume of water and t is the time (120 minutes):

𝑄𝑄 = 𝑉𝑉𝑓𝑓 (Equation 3)

Rearranging Equation 3 and solving for V yields:

𝑉𝑉 = 𝑄𝑄𝑓𝑓 = 82.6 𝑔𝑔𝑚𝑚/ min (120 𝑔𝑔𝑖𝑖𝑖𝑖) 𝑉𝑉 = 9,900 𝑔𝑔𝑚𝑚 = 9.9 𝑚𝑚

Therefore the volume of water required for each test was 9.9 L. 3.2.3 Filter Media The 579 Old Westport Road Treatment Plant uses 18 inches of both anthracite and Greensand on top of 16 inches of graded gravel bed. Since the bench scale filtration column uses a stainless steel wire mesh, the gravel was unnecessary in the bench scale column. Equal heights of anthracite and Greensand at one inch were used in the filter, giving a height of 2 inches of media. This height gave enough room to maintain a constant head of water in the filter without leaking or overflowing. GreensandPlus is used at the 299 Chase Road plant as a replacement for Greensand. In the experiments described in Section 3.2.5, GreensandPlus is one of the media used to test efficiency. The media was soaked in reagent grade water for 24 hours prior to the first test and changed every two tests in order to prevent the need to backwash. 3.2.4 Chemicals Used in Filtration Process At the 579 Old Westport Road Treatment Plant, chemicals are added to the raw water before filtration to remove organic matter, iron, and manganese from the water. The dosages of the chemicals added are shown in Table 14. Bench scale experiments were conducted using the same dosages as the treatment plant, as well as doses above and below the treatment plant values

25

(Sullivan, 2013). Details on the analytical methods for chemical additions are provided in Section 3.3.

Table 14: Dartmouth Water Treatment Plant Chemical Dosing

Chemical Conditions Sodium Hypochlorite (Pre-chlorination) 0.4 mg/L as Cl2 Residual

Kroff KR-C1650 Polymer 1.5– 1.9 mg/L Sodium Hydroxide To reach a pH of about 8.1-8.2

Sodium hypochlorite is added to the raw water to improve the removal efficiency of iron and manganese by the Greensand media. The treatment plant measures the residual of the sodium hypochlorite after the water goes through the filter. The treatment plant also adds 1.5-1.9 mg/L of Kroff KR-C1650 polymer to the raw water to help the organic content precipitate and therefore improve the organic matter removal efficiency of the Greensand media. Lastly, sodium hydroxide is added to the raw water to raise the pH of the water to 8.1-8.2. This ensures that the Greensand media will operate properly. In addition to the chemicals used by the treatment plant, an extra coagulant was added to the raw water to test for the efficiency of further removing organic matter in the water. Aluminum sulfate (alum) was chosen over ferric chloride because there are already high levels of iron in the raw water from the Dartmouth Treatment Plant. In addition, the excess of chlorine in ferric chloride enables more THMs to be formed, so it is becoming less frequently used in public water supply systems. Alum is effective, relatively low cost, readily available and easy to handle, store and apply (U.S. EPA, 2002). 3.2.5 Experiment Conditions The intent of the filtration experiments was to compare operating conditions to optimize removal of TOC/DOC while still removing iron and manganese to needed levels. The current media configuration and operation conditions of the Dartmouth Treatment Plant were used as a baseline for testing. Then, a series of experiments were conducted by modifying different parameters that could affect the removal of iron, manganese, and organic carbon levels. Table 15 shows a summary of the chemical dosage, pH and filter media used in each of these experiments.

26

Table 15: Chemical Dosing and Media Configuration for Bench Scale Experiments

Experiment

Volume of Sample

(mL)

NaOCl (mg/L)

Polymer (mL)

NaOH (mL) pH Filter Media Used

Treatment Plant Conditions 11,000 1.50 0.20 3.25 8.20

Greensand + Anthracite

Quarter Chlorine Residual 10,000 0.75 0.20 5.05 7.60

Greensand + Anthracite

Half Chlorine Residual

12,000 1.37 0.28 3.70 8.12 Greensand + Anthracite

No Chlorine Residual 10,000 0.00 0.20 0.00 7.57

Greensand + Anthracite

Extra Polymer Added 10,000 2.00 0.40 5.80 8.00

Greensand + Anthracite

pH of 7.2 10,000 1.50 0.20 1.00 7.14 Greensand + Anthracite

pH of 8.5 10,000 1.50 0.20 9.70 8.50 Greensand + Anthracite

Greensand 10,000 2.70 0.20 9.80 7.930 Greensand GreensandPlus and Anthracite 9,500 1.40 0.19 5.10 8.20

GreensandPlus + Anthracite

Addition of Alum (30 mg/L) 9,000 1.80 0.20 6.75 8.29

GreensandPlus + Anthracite

3.2.6 Filtration Run Raw water collected at the 579 Old Westport Road Treatment Plant was refrigerated until used. In order to conduct experiments, sodium hypochlorite, polymer, alum, and sodium hydroxide were added to 10 L of well water (see Section 3.3 for solution dosing). The water was passed through the bench scale filter for two hours and effluent samples were collected every 15 minutes to test for UV absorbance (as a surrogate parameter for TOC/DOC levels), chlorine residual, pH, iron, manganese, and TOC/DOC. The concentration of iron, manganese, TOC, and DOC were also tested in the raw water and after the addition of chemicals (pre-filtration). Table 16 shows which parameters were measured at each time throughout the two hour experiments. Section 3.3 describes the methods used to measure all of the mentioned parameters.

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Table 16: Parameters Tested in Bench scale Experiments

3.3 Analytical Methods The following subsections describe the methods used to collect samples, dose chemicals, and measure the water quality throughout the different experiments conducted. 3.3.1 Sodium Hypochlorite The following sections describe the procedure to make the working sodium hypochlorite solution, in addition to determining the correct dosing for the desired sodium hypochlorite residual. 3.3.1.1 Sodium Hypochlorite Solution A sodium hypochlorite solution was made with a target concentration of 1000 mg/L. Using a stock solution of sodium hypochlorite (5.65-6% by volume), the sodium hypochlorite to be used in the bench scale experiments was created. Since the exact concentration of the stock solution was unknown, the concentration was initially assumed to be 50,000 mg/L and was tested to determine its actual concentration. The volume of stock solution needed to create a 1000 mg/L working solution was calculated using Equation 4:

𝑁𝑁1𝑉𝑉1 = 𝑁𝑁2𝑉𝑉2 (Equation 4) In Equation 4, C1 represents the assumed concentration of stock solution (50,000 mg/L). V1 represents the volume to transfer to the volumetric flask. C2 represents the target concentration of the working solution (1,000 mg/L) and V2 represents the volume of the working solution (1,000 mL):

50,000 𝑔𝑔𝑔𝑔𝑚𝑚

(𝑉𝑉1) = 1,000𝑔𝑔𝑔𝑔𝑚𝑚

(1,000 𝑔𝑔𝑚𝑚)

Solving for V1:

Time of Sample (min.) Parameters Measured 0 (Raw Water) pH, TOC/DOC, Iron and Manganese, UV254

0 (Pre-treated Water) pH, TOC/DOC, UV254, Chlorine Residual 15 UV254, Chlorine Residual 30 UV254, Chlorine Residual 45 UV254 60 pH, UV254, Chlorine Residual 75 UV254 90 UV254, Chlorine Residual 105 UV254 120 pH, TOC/DOC, Iron and Manganese, UV254

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𝑉𝑉1 =100

5= 20 𝑔𝑔𝑚𝑚

Using the DR 6000 Hach method 8021, the working solution was diluted by a factor of 1,000 and its concentration tested. The diluted solution had a concentration of 1.09 mg/L. Therefore the concentration of the working solution was 1,090 mg/L. Substituting this number into Equation 4, the actual concentration of the stock solution was calculated:

(𝑥𝑥 𝑔𝑔𝑔𝑔𝑚𝑚

)(20 𝑔𝑔𝑚𝑚) = (1,090𝑔𝑔𝑔𝑔𝑚𝑚

)(1,000 𝑔𝑔𝑚𝑚)

𝑥𝑥 = 54,500 𝑔𝑔𝑔𝑔/𝑚𝑚 Therefore, the concentration in the sodium hypochlorite stock solution was 54,500 mg/L. To create the sodium hypochlorite working solution, Equation 5 was used:

𝑁𝑁𝑠𝑠𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠𝑉𝑉𝑠𝑠𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠 = 𝑁𝑁𝑤𝑤𝑠𝑠𝑤𝑤𝑠𝑠𝑤𝑤𝑤𝑤𝑔𝑔𝑉𝑉𝑤𝑤𝑠𝑠𝑤𝑤𝑠𝑠𝑤𝑤𝑤𝑤𝑔𝑔 (Equation 5) Where Cstock was 54,500 mg/L and a 1,000 mL working stock of 1,000 mg/L was desired.

54,500𝑔𝑔𝑔𝑔𝑚𝑚𝑉𝑉𝐶𝐶ℎ𝑙𝑙𝑠𝑠𝑤𝑤𝑤𝑤𝑤𝑤𝑙𝑙 = �1000

𝑔𝑔𝑔𝑔𝑚𝑚� (1000 𝑔𝑔𝑚𝑚)

Solving for Vstock:

𝑉𝑉𝑠𝑠𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠 = 18.35 𝑔𝑔𝑚𝑚 Therefore, 18.35 mL of stock sodium hypochlorite was added to a 1 L volumetric flask and the solution was brought to the mark to create a working solution with a concentration of 1,000 mg/L. The working solution was used to dose the water with sodium hypochlorite prior to filtration. For two hours of running time, it was calculated that 9.9 L of water would pass through the filter. To simplify calculations and to account for error, 10 L of raw water was prepared. Equation 5 was used to calculate the volume of working stock to add to the 10 L of water to achieve the desired Cl2 dose:

𝑁𝑁𝑤𝑤𝑠𝑠𝑤𝑤𝑠𝑠𝑤𝑤𝑤𝑤𝑔𝑔𝑉𝑉𝑤𝑤𝑠𝑠𝑤𝑤𝑠𝑠𝑤𝑤𝑤𝑤𝑔𝑔 = 𝑁𝑁𝑤𝑤𝑤𝑤𝑓𝑓𝑙𝑙𝑤𝑤𝑉𝑉𝑤𝑤𝑤𝑤𝑓𝑓𝑙𝑙𝑤𝑤 For example, the Cworking was 1,000 mg/L, Cwater was the desired concentration (e.g. 1.5 mg/L), Vwater was 10 L and Vworking was the unknown volume of the working solution.

1,000𝑔𝑔𝑔𝑔𝑚𝑚𝑉𝑉𝑤𝑤𝑠𝑠𝑤𝑤𝑠𝑠𝑤𝑤𝑤𝑤𝑔𝑔 = �1.5

𝑔𝑔𝑔𝑔𝑚𝑚� (10 𝑚𝑚)

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Solving for Vworking:

𝑉𝑉𝑤𝑤𝑠𝑠𝑤𝑤𝑠𝑠𝑤𝑤𝑤𝑤𝑔𝑔 = 0.015 𝑚𝑚 = 15 𝑔𝑔𝑚𝑚 Therefore, 15 mL of working solution was added to the 10 L was sample to achieve a 1.5 mg/L desired dose of sodium hypochlorite. Similar calculations were used for other desired doses. 3.3.1.2 Sodium Hypochlorite Addition to Raw Water The goal for pre-treatment chlorine residual for the Dartmouth Treatment Plant, taken directly after filtration, is 0.4 mg/L. The treatment plant was unable to provide data on the dosage of sodium hypochlorite added. Therefore, various doses were tested and residuals measured to determine the appropriate dose to use for each experiment. Sodium hypochlorite, the appropriate dose of polymer and sodium hydroxide were added to a 10 L sample of raw well water, mixed for two minutes, and then run through the filter. The initial sample that came out of the filter was measured for chlorine residual using the procedure described in Section 3.3.1.3. If the resulting residual was not within 10% of the goal at the start of the test, additional trials were conducted until the residual was correct. This process was repeated for every experiment until the desired chlorine residual was achieved. 3.3.1.3 Chlorine Residual Measurement The U.S. EPA regulates disinfectants based on the MRDL, this regulation includes chlorine. Chlorine residual was measured on a Hach DR 6000 using DPD Free Chlorine Reagent Powder Pillows (25 mL sample) and 1 inch, 25 mL glass cells. One cell was filled with 25 mL of sample, cleaned with a Kimwipe and inserted into the instrument to zero it. A second sample cell was filled with 25 mL of sample, a Powder Pillow was added, and the cell was mixed for 20 seconds. The cell was cleaned and read within 30 seconds of adding the Powder Pillow. The chlorine residual was measured once after the pre-treatment chemicals were added, prior to filtration, again at the 15-minute mark, and at every 30-minute mark after that. The chlorine residual was measured to compare the levels for different filter designs and to the MRDL. 3.3.2 Polymer The following sections describe the dosing methods used to achieve the same concentration of polymer in the bench scale experiment as the Dartmouth Treatment Plant. \ 3.3.2.1 Polymer Solution At the Dartmouth Treatment Plant, Kroff KR-1650 polymer is diluted at a ratio of 5 gallons of polymer to 60 gallons of water. This polymer solution was taken from the 579 Old Westport Road plant and used as the stock solution for testing.

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3.3.2.2 Polymer Addition In order to calculate the appropriate amount of Kroff KR-C1650 polymer to add, the Dartmouth Chemical Treatment Report for the month of August 2013 was used. This report specifies the number of gallons treated per day and gallons of diluted polymer solution used per day. The total amount of water treated for the month (30,790,000 gallons) and gallons of diluted polymer (600 gallons) used for the month were also given. These amounts were used to calculate diluted polymer addition for laboratory experiments by Equation 6:

𝑃𝑃1𝑉𝑉1

= 𝑃𝑃2𝑉𝑉2

(Equation 6)

Where 𝑃𝑃1 is the amount of diluted polymer used (gallons), 𝑉𝑉1 is the amount of water treated (gallons), 𝑉𝑉2 is the volume of water treated in laboratory experiments (10 L or 2.64172 gallons) and 𝑃𝑃2 is the amount of diluted polymer solution used in laboratory experiments.

600 𝑔𝑔𝑁𝑁𝑁𝑁𝑁𝑁𝑓𝑓𝑖𝑖𝑒𝑒30, 790,000 𝑔𝑔𝑁𝑁𝑁𝑁𝑁𝑁𝑓𝑓𝑖𝑖𝑒𝑒

=𝑃𝑃2

2.64172 𝑔𝑔𝑁𝑁𝑁𝑁𝑁𝑁𝑓𝑓𝑖𝑖𝑒𝑒

𝑃𝑃2 = 5.14 × 10−5 gallons = 0.195 mL diluted polymer solution per 10 L of water. Similar calculations were repeated using data from the Dartmouth Chemical Treatment Report in November 2013 and found that 0.21 mL diluted polymer sample should be used per 10 L of water treated in laboratory experiments. Thus, 0.2 mL of diluted polymer sample was used for every 10 L of treated well water (or an adjusted amount when polymer dose was varied in an experiment). 3.3.3 Sodium Hydroxide The following section describes how the sodium hydroxide working solution was made and how the added amount was determined. 3.3.3.1 Sodium Hydroxide Solution A 1 N stock solution of sodium hydroxide was created. Forty grams of sodium hydroxide pellets were measured on an analytical scale and added to a volumetric flask. Reagent grade water was then added up to the 1 L line of the volumetric flask. It was placed on a mixer with a stir bar and mixed until dissolved. 3.3.3.2 Sodium Hydroxide Addition In order to achieve the desired pH of pre-treated water, sodium hydroxide was added after sodium hypochlorite and polymer additions. 1 N sodium hydroxide was added in increments of 1 mL or less. After each addition, the water sample was mixed and the pH measured. This process

31

was repeated until the desired pH (8.1-8.2) was reached. A pH of 8.0-8.3 was considered acceptable. 3.3.4 Aluminum Sulfate This section describes the procedure to make the working alum solution, in addition to determining the correct dose and treatment plant requirements. An alum working solution with a concentration of 30 g/L was made. The volume of stock solution needed for a 30 mg/L dose of alum was calculated using Equation 7:

𝑁𝑁𝑠𝑠𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠𝑉𝑉𝑠𝑠𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠 = 𝑁𝑁𝑠𝑠𝑤𝑤𝑔𝑔𝑔𝑔𝑙𝑙𝑙𝑙𝑉𝑉𝑠𝑠𝑤𝑤𝑔𝑔𝑔𝑔𝑙𝑙𝑙𝑙 (Equation 7) Cstock was 30 g/L and a 10 L sample dosed with 30 mg/L alum was desired.

30,000𝑔𝑔𝑔𝑔𝑚𝑚𝑉𝑉𝑠𝑠𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠 = 30

𝑔𝑔𝑔𝑔𝑚𝑚

10 𝑚𝑚

Solving for VStock:

𝑉𝑉𝑠𝑠𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠 = 0.01 𝑚𝑚 = 10 𝑔𝑔𝑚𝑚 Therefore, 10 mL of stock alum was added to create a dose of alum with a concentration of 30 mg/L. The stock solution was used to dose the water with alum prior to filtration. 3.3.5 pH One factor that affects THM formation in water systems is pH. Samples were tested using a Fisher Scientific Accumet AB15 pH Meter (Fisher Scientific, Waltham, MA). Before measurement, the meter was calibrated using three pH buffers with known values of 4, 7, and 10. Prior to and after each reading, the probe was rinsed with reagent grade water and then placed into the sample until a stable reading for pH was reached. The probe was stored in an electrode storage solution when not in use. 3.3.6 Temperature Temperature was measured due to its correlation with THM levels. High temperatures are a factor in THM formation in water systems. The temperature of water samples from the distribution system were taken using a Traceable© Thermometer. Temperatures from well water samples were obtained from readings on electronic well monitors on September 11 and October 11. On January 23, a Traceable© Thermometer was used.

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3.3.7 Organic Carbon TOC and DOC were measured because high levels of TOC and DOC present during disinfection could lead to the formation of THMs and other DBPs. The TOC and DOC of well and distribution system samples were measured as described in the following sections. 3.3.6.1 Glassware All glassware used for TOC/DOC analysis was acid washed. Glassware was washed with soap and hot water, thoroughly rinsed and then acid washed in 20% sulfuric acid bath for at least one hour. Glassware was then rinsed three times with reagent grade water and allowed to dry. 3.3.6.2 Sample Preservation Water samples were preserved prior to analysis. Samples were preserved to reduce the rate of microbiological growth and prevent any microorganisms from metabolizing the organics for food (Wallace, 2003). For TOC, 40 microliters of 6 N HCl was pipetted into each vial. Then, approximately 40 mL of